First-order transition to a noncollinear antiferromagnetic structure in U 2 Rh 3 Si 5

摘要: We have determined the antiferromagnetic structure of monoclinic U{sub 2}Rh{sub 3}Si{sub 5} and temperature dependence magnetically ordered moment {mu} via single-crystal neutron diffraction. The value exhibits a sharp discontinuity at ordering T{sub N}=25.5 K, jumping from 1.6{mu}{sub B} to zero within narrow interval [{Delta}T{sub N}=0.2 {mu}(9 K)=2.35{mu}{sub B}]. This demonstrates first-order nature transition. is noncollinear arrangement eight uranium magnetic moments crystallographic unit cell. are oriented parallel nearest-neighbor U-Rh bonds, creating uniaxial (Ising-type) behavior, with canted local easy axes. lattice parameters, as high-resolution x-ray diffraction, exhibit pronounced discontinuities N}. These data demonstrate strong magnetoelastic coupling. {copyright} {ital 1997} American Physical Society}